Tommy Rowe will miss the rest of this season and faces a race against time to be fit for the start of the next campaign after going under the knife.
Rowe was left out of the matchday squad for Saturday's clash with Oxford United.
And he underwent an operation earlier in the week to repair a hamstring problem that he had been suffering with for some time.
Boss Darren Ferguson said: "Tommy is out. He's had an operation.
"It's a tendon on his hamstring. It's an operation he should have had maybe four weeks ago.
"But he wanted to keep playing.
"He went to see the surgeon on Thursday and he'd done more damage.
"He will be out for four months.
"Tommy shouldn't have been playing and there's one or two more that are hanging in there which shows the mentality of the players.
"With Tommy we had to make a decision on how long we could play him."
On whether Rowe will be fit for the start of the 2018/19 campaign, Ferguson said: "I don't know.
"He will get a pre-season because he'll be in the rehab phase.
"My physio was saying it had to be done but I was delaying it.
"We spoke to Tommy after every game and he felt all right.
"But at this stage there was no choice after the specialist saw it again.
"It would have gone and if that would have happened it would have been a real problem."
Prior to Saturday, Rowe had missed just one league game in his two years with the club.